| Parasitic wasps are important biological control resources due to their diversity,phenotypic plasticity and wide host range.Pteromalus puparum parasitizes a variety of lepidopteran pests and is the dominant parasitoid of Pieris rapae pupae.The parasitic potential of parasitic wasps is closely related to their lifespan.Extending the lifespan of parasitic wasps has significant benefits on field control and economic efficiency.The lifespan of P.puparum is highly plastic with changes in environmental factors.To understand the longevity regulating mechanisms of P.puparum,this study investigated the effects of three factors of aging,including nutritional conditions,heat stress,and virus infection.The main findings are as follows.1.Annotation of lifespan-related genes of P.puparumCombining genomic and transcriptomic data,229 putative lifespan-related genes were predicted from P.puparum genome based on known lifespan-related gene sequences.These genes function in four signaling pathways,including the IIS-PI3K/Akt pathway,TOR pathway,MAPK/ERK pathway and AMPK pathway,along with three physiological processes,including autophagy,stress response and metabolism.We predicted the conserved domain structures of these genes and analyzed their expression patterns.Amino acid sequence alignment and domain structure analysis showed that most genes are conserved in six orders of insects.2.Effects of sugar sources on adult lifespan,survival and related gene expression of P.puparumWe assessed the effect of feeding sucrose and honey on the lifespan of P.puparum in the range 0-40%(w/v).The results indicated a statistically significant positive effect of sucrose and honey solutions on the lifespan of P.puparum female adults.Correlation analyses confirmed a strong positive correlation between high concentrations of sugar and extended lifespan.The optimum concentration of sucrose solution for wasps was 20%,while 10%for honey.Then,we examined the expression patterns of 15 lifespan-related genes.The results showed that the relative expression levels of 14 genes were significantly correlated with the mean lifespan of sucrose-fed wasps,and six genes correlated with the mean lifespan of honey-fed wasps.In addition,the models for lifespan prediction were constructed.3.Effect of heat stress on the adult lifespan of P.puparumBased on the high-quality transcriptome data obtained from RNA sequencing,we analyzed the gene expression patterns of female adult P.puparum in 25? and 35?environments.The results showed that the gene expression of P.puparum changed significantly from 6 h of treatment in response to heat stress,gradually accumulating to achieve a dramatic effect by 5 days of treatment.The gene expression patterns were clearly divided into two group:short-term and long-term.The differentially expressed genes for short-term heat stress were mainly involved in signaling pathways such as antigen processing and presentation,multispecies lifespan regulation and endoplasmic reticulum protein processing pathways.The differentially expressed genes of long-term heat stress are mainly involved in several disease and cancer signaling pathways.In addition,nine hub genes were discovered using weighted gene co-expression network analysis.After validation of the transcriptome data,the predicted hub genes were verified by RNA interference and three novel lifespan-related genes were identified,namely PpXAP5,PpELL and PpCathL.4.Effect of PpNSRV-1 on the adult lifespan of P.puparumBased on high-quality transcriptome data obtained from RNA sequencing,we analyzed gene expression in female adult P.puparum with and without the virus PpNSRV-1.The results showed a low number of differentially expressed genes and no significant enrichment of gene ontology(GO)functions and KEGG signaling pathway.Using gene weighted co-expression network analysis,we identified a module highly associated with virus-induced longevity traits and screened for hub genes in the gene co-expression network.The hub genes may function in the autophagy pathway,p53 signaling pathway and amoebiasis pathway.5.The role of lifespan regulating pathway inhibitors on the adult lifespan of P.puparumSeveral inhibitors were selected for oral delivery to P.puparum using annotated lifespan-related genes and newly identified lifespan-related genes in the transcriptomes as target genes.Three inhibitors were found to significantly prolong the adult lifespan of P.puparum females,namely Trametinib,Rapamycin and Cathepsin Inhibitor.They prolonged the mean lifespan of P.puparum by 34%,56%and 51%,respectively. |
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